// // This code is part of Document Solutions for PDF demos. // Copyright (c) MESCIUS inc. All rights reserved. // using System; using System.IO; using System.Drawing; using GrapeCity.Documents.Pdf; using GrapeCity.Documents.Pdf.Graphics; using GrapeCity.Documents.Text; using GrapeCity.Documents.Drawing; using GCTEXT = GrapeCity.Documents.Text; using GCDRAW = GrapeCity.Documents.Drawing; namespace DsPdfWeb.Demos { // This sample demonstrates how to use GcPdfGraphics.SoftMask // to draw semi-transparently and specify clipping. public class SoftMask1 { public int CreatePDF(Stream stream) { var doc = new GcPdfDocument(); var page = doc.NewPage(); var g = page.Graphics; var rc = Common.Util.AddNote( "GcPdfGraphics has a SoftMask property, which allows creating a mask with a FormXObject, " + "draw on that object's Graphics using any supported drawing methods " + "(including semi-transparent drawing), and then use the result as a mask when drawing " + "on the document's pages. Only the alpha channel from the mask is used. " + "Solid areas do not mask, transparent areas mask completely, " + "semi-transparent areas mask in inverse proportion to the alpha value.", page); var rMask = new RectangleF(0, 0, 72 * 5, 72 * 2); var rDoc = new RectangleF(rc.Left, rc.Bottom + 36, rMask.Width, rMask.Height); var softMask = SoftMask.Create(doc, rDoc); var smGraphics = softMask.FormXObject.Graphics; smGraphics.FillEllipse(rMask, Color.FromArgb(128, Color.Black)); smGraphics.DrawString("SOLID TEXT", new TextFormat() { Font = StandardFonts.HelveticaBold, FontSize = 52, ForeColor = Color.Black }, new RectangleF(rMask.X, rMask.Y, rMask.Width, rMask.Height), TextAlignment.Center, ParagraphAlignment.Center, false); var rt = rMask; rt.Inflate(-8, -8); // Color on the mask does not matter, only alpha channel is important: smGraphics.DrawEllipse(rt, Color.Red); g.SoftMask = softMask; g.DrawImage(GCDRAW.Image.FromFile(Path.Combine("Resources", "Images", "reds.jpg")), rDoc, null, ImageAlign.StretchImage); // NOTE: it looks like some PDF viewers (such as built-in browser viewers) // do not handle changing soft masks correctly unless the mask is reset prior // to assigning a new one, hence this: g.SoftMask = SoftMaskBase.None; rDoc.Offset(0, rDoc.Height + 12); rDoc.Width = rc.Width; rDoc.Height = 36; rMask.Height = rDoc.Height; // Draw a string on mask with increasing alpha values: for (int alpha = 16; alpha <= 255; alpha += 32) { softMask = SoftMask.Create(doc, rDoc); smGraphics = softMask.FormXObject.Graphics; smGraphics.DrawString($"Text drawn on mask with alpha {alpha}.", new TextFormat() { Font = StandardFonts.HelveticaBold, FontSize = 24, ForeColor = Color.FromArgb(alpha, Color.Black) }, new RectangleF(rMask.X, rMask.Y, rMask.Width, rMask.Height), TextAlignment.Leading, ParagraphAlignment.Center, false); g.SoftMask = softMask; g.DrawImage(GCDRAW.Image.FromFile(Path.Combine("Resources", "Images", "reds.jpg")), rDoc, null, ImageAlign.StretchImage); g.SoftMask = SoftMaskBase.None; rDoc.Offset(0, rDoc.Height); } // Done: doc.Save(stream); return doc.Pages.Count; } } }